Which of the following gases has the highest calorific value?

Correct option is A

The gas with the highest calorific value is hydrogen. It has the highest calorific value among the given options, ranging around 142 MJ/kg (Megajoules per kilogram).
Methane: The main component of natural gas, methane has a calorific value of around 55 MJ/kg.
Natural gas: The composition of natural gas can vary slightly, but it's primarily methane with some other hydrocarbons. Its calorific value falls around 42-55 MJ/kg depending on the specific composition.
LPG (Liquefied Petroleum Gas): A mixture of hydrocarbon gases like propane and butane, LPG has a calorific value of around 46-51 MJ/kg.
Therefore, while all these fuels are combustible and release heat during burning, hydrogen offers the highest amount of energy per unit of mass.